Effects of dopamine on whole kidney function and proximal transtubular volume fluxes in the rat

The renal effects of dopamine were studied using clearance and micropuncture techniques in rats. Intravenous infusion of dopamine (4.7 - 10(-6) mol - kg-1 - h-1) increased glomerular filtration rate and renal blood flow. Renal blood flow was measured by an electromagnetic flowmeter. The increase in filtered fluid and sodium was nearly completely matched by increased tubular reabsorption. Thus, only a small rise in urine flow and in urinary sodium excretion was observed. The micropuncture experiments using the split oil droplet method of Gertz demonstrated a stimulation of the transepithelial fluid transfer after injection of dopamine (10(-4) M) into the proximal tubular lumen. This effect was abolished by simultaneous injection of propranolol (10(-3) M) which, by its own, did not affect transtubular volume fluxes. It is concluded that dopamine, by stimulation of beta-adrenoceptors, may increase reabsorptive capacity of the proximal tubular epithelium independent of changes in renal hemodynamics.